Pulverizer



Nov. 27, 1945. 3,3, so 2,389,844

PULVERI'ZER Filed Sept. 19, 1942 2 Sheets-Sheet 1 I 62 y) 79 u 20 q)INVEN] OR.

BY Gear 8 B Eberso/e I ATTORNEY Nov. 27, 1945. e. B. EBERSOLE 2,389,844

PULVERI ZER Filed Sept. 19, 1942 2 Sheets-Sheet 2 III ' INVENTOR.

By 995. Ebersole ATTORNEY Patented Nov. 27, 1945 mvmuzan George B.Ebersole, Akron, Ohio, asslgnor to The Babcock & Wilcox Company, JerseyCity, N. J., a corporation of New Jersey Application September 19, 1942,Serial No. 458,935

13 Claims.

The present invention relates to'the construction and operation ofpulverizers of the type having rolling grinding elements located betweenoperating relatively movable grinding rings and particularly topulverizers of the type described designed for pulverizing coal, cementmaterials and the like at moderate capacities and in which thepulverized material is removed from the pulverizer in suspension in agaseous carrier medium, such as the pulverizer shownv in the Schwartz U.S. Patent No. 2,275,595.

The general object of my invention is the provision of a pulverizer ofthe type described which is characterized by an improved constructionand arrangement of the parts in the air entranc area of the pulverizer.A further and more specific object is the provision of an improvedpulverizer construction for disposing of ungrindable portion of thematerial undergoing pulverization, such as the pyrites constituents ofcoal, with a minimum wear on the pulverizer parts. A further specificobject is the provision of an improved pulverizer construction forpreventing material from working inwardly between certain rotary andstationary parts of the pulverizer, and thereby increasing the load onthe drive mechanism of the pulverizer.

The various features of novelty which characterize my invention arepointed out with particularity in the claim annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described preferred embodimentsof my invention.

Of the drawings:

Fig. 1 i a sectional elevation of a pulverizer constructed in accordancewith my invention;

Fig. 2 is an enlarged sectional View of some of the parts shown in Fig.1 at a different location;

Fig. 2 is a horizontal section taken on the line 33 of Fig. 2;

Fig. 4 is a fragmentary sectional elevation illustratin a modifiedconstruction; and

Figs. 5 and 6 are views similar to Fig. 4 illustrating furthermodifications.

The pulverizer illustrated has a substantially cylindrical sectionalhousing i0 having a base section II with a slightly conical bottom platemounted on a foundation H. The base section contains the pulverizerdrive assembly including a horizontal pinion shaft l3 arranged to drivea vertical drive shaft l4 axially arranged in the housing. The driveshaft I4 extends upwardly through bearings arranged in a base plate l5forming the top of the base section i I. The upper section l6 of thehousing is of substantially cylindrical form and detachably secured inthe base section plate IS. The upper housing section encloses thegrinding part of the pulverizer, which comprises a drive yoke ll ofgenerally conical form keyed on the upper part of the drive shaft M. Anannular lower grinding ring I9 is supported on and keyed to the lowerouter portions of the drive yoke. The upper face of the grinding ring 19is shaped to form a track for a circular row of rolling grindingelements 20, preferably ball of wear resistant alloy steel. The balls 20support an upper grinding ring 2| having a ball track formed in itslower face. An annular spider 22 mounted on the upper ring is providedwith lugs 23 arranged in guides on the inner wall of the housing sectionIt for preventing rotation, but permitting vertical movement, of thespider and upper grinding ring. A esilient grinding pressure is exerteddownwardly on the grinding parts by coil springs 24 engaging the spider,

The material to be pulverized i supplied through a feed spout 25 to theinner side of the upper grinding rin and ball row and deposits on theinclined upper surface of the drive yoke H, being distributed throughoutthe grinding area by the rotation of the drive yoke and associatedparts. The material fiows outwardly over the upper surface of the yokeand lower grinding ring, is pulverized between the relatively movingballs and grinding rings, and discharge at the outer edge of the lowergrinding ring I9.

The pulverizer disclosed is of the air swept type having an annularstream of carrier air passing upwardly through the pulverizer grindingzone and through a material classifier 30 to the pulverizer outlet 3|.The carrier air is normally preheated and supplied under pressure by a.suitable forced draft fan to an annular wind box 32 surrounding thelower part of the housing section It. The annular stream of carrier airpasses into the pulverizer housing through passages hereinafterdescribed, and upwardly through a Venturi-shaped throat passage 33formed between the outer side of the lower grinding ring I 9 and anannular throat plate 35 secured to the inside of the housing and shapedto provide a high velocity stream of air sweeping past the dischargeside of the lower grinding ring, the flow areas and air velocities beingproportioned to prevent any pulverized material within the designeddensity range from dropping through the throat and cloasins the enteringair passages. The air stream does not prevent the downward discharge ofrelatively unpulverizable mall size particles or high density, such asis present in the pulverizetion of coal having a high pyrites or sulphurcon tent. In such cases the heavy particles tend to drop through thethroat against the rising air stream and into the subjacent portion orthe pulverizer. A portion of the throat ring is also provided with asegmental spring-pressed relief gate 86 for the passage of any pieces oiunpulverizable foreign material, such as tramp iron, and allowing thesame to drop into' the lower portion or the housing. At a point oppositethe location of the relief gate 35", the base section of the housing isprovided with a compartment 40 for the collection of such unpulverizablematerial. The compartment 40 communicates with the grinding zone througha small opening 4| in the housing base plate below which a slidable gate42 is mounted and manually operated through a rack and pinion system 43to open and close the opening 4|,

In accordance with my invention the pulverizer parts are constructed tofacilitate the elimination oi unpulverizable material without excessivewear on the material contacted parts, such as tends to occur when sweepsor plows are mounted on the lower grinding ring for moving theunpulverizable material to the discharge opening 4|. Such material wouldordinarily drop through the air throat onto the upper surface of thebase plate, and unless removed would tend to work its way into the spacebetween the base plate and rotating lower grinding ring or yoke,increasing the frictional wear on those parts. Sulphur balls in thisarea are also highly objectionable as they tend to freeze the rotatingparts to the base plate when the pulverizer is shut down and therebyincrease the load on the drive mechanism when again starting up. Thisfreezing of the parts is accentuated by the thermal contraction of theseparts when no longer subject to the preheated air I or the heatdeveloped during the grinding operation.

In the construction illustrated in Figs. 1-3 the rotating drive partsand base plate are so constructed that any such action is minimized. For

.this purpose the drive yoke I1 is terminated radially short of theouter side of the lower grinding ringl9, and the latter provided with adepending annular skirt 50 extending downwardly beyond the outer edge ofthe yoke to a point having a slight clearance from the base plate I5.The lower end of the skirt projects outwardly in the form of a lip 5| toprovide a surface on which material dropping into that area can besupported and carried around towards the discharge opening 4|. Thesupporting. action of the lip is facilitated by the relative arrangementof a circular series or segmental filler plates 55 located on theinclined bottom of the wind box and extending downwardly towards theskirt lip 5| to form a narrow annular slot or gap 56 therebetween. Theplates 55 tend to direct any material depositing thereon downwardly ontothe rotating lip. The gap 56 is enlarged immediately above the dischargeopening 4| by shortening the corresponding plate 55, as shown in Fig. 1.

The depending annular skirt on the lower grinding ring has its innerside arranged at an angle to and spaced from the outer side of the driveyoke II. This construction provides an upwardly tapering space 51 whichis occupied by an upwardly tapering annular bafiie ring 58 on the baseplate l5 proportioned to form a narrow annular inverted V -shaped spacebetween the stationary and rotating parts. 'This baille constructionobstructs'the movement 01 any material into the space between the bottomof the drive yoke and base plate.

The angular rotation of th lower grinding ring is indicated by thedirection of the arrow in Fig. 3. Consequently the pulverized coalleaving the upper'suriace of the grinding ring tends to flow over theouter edge thereof at an angle to but in the same general direction asthe rotation of the lower ring. The pressure drop through the throatsection of the pulverizer can beappreciably reduced when the air fromthe wind box enters the pulverizing zone in approximately the samedirection as the flow of fuel. For this purpose adjoining segmentaliiller plates 55 are provided with curved vertical blade sections 6|]and 6| relatively arranged thereon to form a circular series ofoutwardly-tapering composite curved blades or vanes 62 forming passages63 therebetween curving inwardly in the direction of rotation of thelower grinding ring. The vanes 62 terminate at their inner ends oppositeposts 64, between the plates 55 and forming spaced continuations of thepulverizer casing and the discharge ends of the air passages. With thisvane arrangement the enterin air is distributed about the circumferenceof the throat section and directed obliquely to the normal direction ofpulverized material leaving the grinding zone, i. e. at an angle ofapproximately 45 thereto. Confining the entering air to the curvingpassages 63 facilitates the movement of the unpulverizable material downthe plates 55 and onto the tip 5|, and thus to the discharge opening 4|.

While in Figs. l-3 the plates 55 formin the stationary seal ring for thegrinding ring skirt lip 5| are formed integrally with the vanes 60 and6|, the seal ring can be separately formed,

- above the discharge opening 4| to permit the material carried by thelip 5| to discharge thereto. In this modification the baflle ring 58 isseparately formed and secured to the base plate I5 to provide a steeplyinclined annular space between the baille ring and grinding ring skirt.

In .the modified constructions illustrated in Figs. 5 and 6, the annularsupporting lip 5| is formed on a peripheral portion of the drive yokewhich extends beyond the outer side of the grinding ring I9. Theprojecting portion can be integrally formed as shown in Fig. 5 or by acircumferential band 15 welded to the periphery of the drive yoke, asshown in Fig. 6. Ahorizontally arranged seal ring Hi is secured to thepulverizer casing opposite the lip 5| in Fig. 5

' lower grinding ring at an oblique angle thereto due to the rotation ofthe ring. The pulverized material is swept up by the annular air streamentering through the passages 63 and swirling upwardly through the airthroat, the materialladen air then passing upwardly to the classifierand pulverizer outlet. The particles of material not swept up by the airstream due to their size or density fall through the air throat into theair entrance area at the outer side of the lower grinding ring. Theseparticles collect on the bottom of this section and are carried aroundby the lip formed on the lower grinding ring skirt or drive yoke untilthe recessed portion of the seal ring is reached and the particlespermitted to fall into the discharge opening II. The air stream swirlingin the direction of rotation of the lower. grinding ring aids themovement of these particles towards the discharge opening. Thearrangement of the supporting lip on the lower grinding ring isespecially advantageous as this member is normally mad with a harderwearing surface than the Yoke, with corresponding longer life, andbecause replacement of the ring'due to excessive wear in the track areaalso restores the original lip outside diameter. With the described lipand seal ring constructions, the bottom of the pulverizer is keptcomparatively clean of foreign material.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best forms of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of the invention may sometimes be used to advantage without acorresponding use of other features. In the claims, the word "air isintended to generically cover any gaseous carrier medium suitable forremoving pulverized material in the manner described.

I claim:

1. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor efiecting relative movement of said grinding elements and ring,means for delivering material to be pulverized to the inner side of saidgrinding elements, means for directing a stream of air upwardly past theouter side of said grinding ring to sweep up pulverized materialdischarging therefrom including an air supply chamber Opening to saidcasing at the outer side of said grinding ring and below the level ofsaid grinding elements a discharge opening for unpulverized material atthe outer side of said grinding ring and adjacent said air entranceopening, and an outwardly projecting annular lip member at the outerside of and rotating with said grinding ring, said lip member having anupper surface portion horizontally arranged and in position to receiveunpulverized material discharged from" said grinding ring and carry saidunpulverized material towards said discharge opening.

2. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor efiecting relative move-' ment of said grinding elements and ring,means for delivering material to be pulverized to the inner side of saidgrinding elements, means for directing a stream of air upwardly past theouter outer side of said grinding ring and below the level of saidgrinding elements, a'discharge opening for unpulverized material at theouter side of said grinding ring and adjacent said air entrance opening,an outwardly projecting annular lip at the outer side of and rotatingwith said grinding ring shaped and arranged for carrying unpulverizedmaterial to said discharge opening, and means forming a stationary sea1ring in the space between said lip and casing and cooperating with saidlip to form a narrow annular slot therebetween.

3. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor effecting relative movement of said grinding elements and ring,means for delivering material to be pulverized to the inner side of saidgrinding elements, means for directing a stream of air upwardly past theouter side of said grinding ring to sweep up pulverized materialdischarging therefrom including an air supply chamber opening to saidcasing at the outer side of said grinding ing and below the level ofsaid grinding elements, a discharge opening for unpulverized material atthe outer side of said grinding ring and adjacent said air entranceopening, and a depending skirt on the outer side of said grinding ringhaving an outwardly projecting lip with an upper surface portionhorizontally arranged and in position to receive unpulverized materialdischarged from said grinding ring and carry said unpulverized materialto said discharge opening.

4. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor efiecting relative movement of said grinding elements and ring,means for delivering material to be pulverized to the inner side of saidgrinding elements, means for directing an annular stream of air upwardlypast the outer side of said grinding ring to sweep up pulverizedmaterial discharging therefrom including an air supply chamber openingto said casing at the outer side of said grinding ring and below thelevel of said grinding elements, a discharge opening for-unpulverizedmaterial at the outer side of said grinding ring and adjacent said airentrance opening, 3, depending skirt on the outer side of said grindingring having an outwardly projecting lip with an upper surface portionhorizontally arranged and in p0 sition to receive unpulverized materialdischarged from said grinding ring and carry said unpulverized materialto said discharge opening, and means forming a stationary seal ring inthe space between said skirt and casing.

5. A pulverizer comprising a casing having a base plate and an outletfor material-laden air at its upper end and enclosing a horizontallyarranged rotary grinding ring, rolling grinding elements on saidgrinding ring, an annular drive yoke superjacent said base plate andsupporting said grinding ring, means for delivering material to bepulverized to the inner side of said grinding elements, means fordirecting a stream of air upwardly past the outer side of said grindingring to sweep up pulverized material discharging therefrom including anair supply chamber opening to said casing at the outer side of saidgrinding ring and below the level of said grinding elements, a dischargeopening for unpulverised material in said base plate at the outer sideor said drive yoke and adjacent said air entrance opening, and anoutwardlymrojecting lip on the outer side or said drive yoke, said liphaving an upper surface portion horizontally arranged and in position toreceive unpulverized material discharged from said grinding ring andcarry said unpulverized material toward said dis charge opening.

6. A pulverizer comprising 'a casing having a base plate and an outletfor material-laden air at its upper end and enclosing a horizintallyarranged rotary grinding ring, rotary grinding elements on said grindingring. an annular drive yoke superiacent said base plate and supportingsaid grinding ring, means for delivering material to be pulverized tothe inner side of said grinding elements, means for directing a streamof air upwardly past the outer side of said grind: ing ring to sweep uppulverized material discharging thereirom including an air supplychamber opening to said casing at the outer side of said grinding" ringand below the level of said grinding elements, a discharge opening idrunpulverized material in said base plate at the outer side of saidgrinding ring and adjacent said air entrance opening, a depending skirton the outer side of said grinding ring beyond said drive yoke, and abaille ring on said base plate projecting upwardly into the spacebetween said skirt and drive yoke to obstruct the inward flow ofunpulverized material.

7. A pulverizer comprising a casing having a base plate and an outletfor material-laden air at its upper end and enclosing a horizontallyarranged rotary grinding ring, rolling grinding elements on saidgrinding ring,-an annular drive yoke superjacent' said base plate andsupporting said grinding ring, means for delivering material to bepulverized to the inner side or said grinding elements, means fordirecting an annular stream of air upwardly past the outer side of saidgrinding ring to sweep up pulverized material discharging therefromincluding an air supply chamber opening to said casing at the outer sideof said grinding ring and below the level of said grinding elements, adischarge opening for unpulverized material in said base plate at theouter side of said grinding ringand adjacent said air entrance opening,a depending skirt on the outer side of said grinding ring beyond saiddrive yoke and having means for carrying unpulverized material to saiddischarge opening, means forming a stationary seal ring in the spacebetween said skirt and casing, and a baiiie ring on said base plateprojecting upwardly into the space between said skirt and drive yoke toobstruct the inward flow of unpulverized material between said baseplate and drive yoke.

8. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor eflecting relative movement of said grinding elements and ring,means for delivering material to be pulverized to the inner side of saidgrinding elements, means for directing an annular stream oi air upwardlypast the outer side of said grinding ring to sweep up pulverizedmaterial discharging therefrom including,an air supply chamber and anair entrance opening from said chamber to said casing at the outer sideor said grinding ring and below the level of said grinding elements, and

assaass a circular series or curved vanes in said air entrance openingdefining air passagescurving inwardly in the normal direction 01'rotation of said grinding ring.

9. A pulverizer comprising a casing having an outlet for material-ladenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding rin means foreflecting relative movement of said grinding elements and ring, meansfor delivering material to bepulverized to the inner side of saidgrinding elements, means for directing an annular stream or air upwardlypast the outer side of said grinding ring to sweep up pulverizedmaterial discharging therefrom including an air supply chamber openingto said casing at the outer side. of said grinding rin and below thelevel 01' said grinding elements, a discharge opening for unpulverizedmaterial at the outer side of said grinding ring and adiacent said airentrance opening, a depending skirt on the outer side of said grindingring having means for carrying unpulverized material to said dischargeopening, and a circular series of curved vanes in said air entranceopening defining air passages curving inwardly in the normal directionof rotation 0! said grinding ring.

10. A pulverizer comprising a casing having an outlet for material-Jadenair at its upper end and enclosing a horizontally arranged rotarygrinding ring, rolling grinding elements on said grinding ring, meansfor eflecting relative movement of said grinding elements and ring.means ior delivering material to be pulverized to the inner side orsaidgrinding elements, means for directing an annular stream 01' aiupwardly past the outer side of said grinding ring to sweep uppulverized material discharging therefrom including an air supplychamber opening to said casing at the outer side of said grinding ringand below the level or said grinding elements, a discharge opening forunpulverized material at the outer side oi said grinding ring andadjacent said air entrance opening, a depending skirt on the outer side01' said grinding ring havin means for carrying pulverized material tosaid discharge opening, a circular series of plates in said air entranceopening forming a stationary seal ring surrounding said skirt, and'acircular series of curved vanes on said plates defining air passagescurving inwardly in the normal direction of rotation of said grindingring.

11. A pulverizer comprising a casing having a stationary base plate andan outlet for materialladen air at its upper end and enclosing ahorizontally arranged rotary grinding ring, rotary grinding elements onsaid grinding ring, an annular drive yoke superjacent said base plateand supporting said grinding ring, means for deliv- -ering material tobe pulverized to the inner side of said grinding elements, means fordirecting a stream of air upwardly past the outer side of said grindingring to sweep up pulverized ma- ,tween said drive yoke and base plate.

- 12. A pulverizer comprising a casing having a stationary base plateand an outlet for materialladen air at its upper end and enclosing ahorizontally arranged rotary grinding ring, rotary grinding elements onsaid grinding ring, an annular drive yoke superjacent said base plateand supporting said grinding ring, means for delivering material to bepulverized to the inner side of said grinding elements, means fordirecting a stream of ai upwardly past the outer side of said grindingring to sweep up pulverized material discharging therefrom including anair supply chamber opening to said casing at the outer side of saidgrinding ring and below the level of said grinding elements, a dischargeopening fo unpulverized material in said base plate at the outer side ofsaid grinding ring and adjacent said air entrance opening, and a balilering on said base plate projecting upwardly into the space below saidgrinding ring and arranged to obstruct the inward fiow of unpulverizedmaterial between said drive yoke and base plate.

13. A pulverizer comprising a casing having a stationary base plate andan outlet for materialladen air at its upper end and enclosing ahorizontally arranged rotary grinding ring, rolling grinding elements onsaid grinding ring, a circular drive yoke superjacent said base plateand supporting said grinding ring, means for delivering material to bepulverized to the inner side of said grinding elements, means fordirecting a stream of air upwardly past the outer side of said grindingring to sweep up pulverized material discharging therefrom including anair supply chamber and an air entrance opening from said chamber to saidcasing at the outer side of said grinding ring and below the level ofsaid grinding elements, a discharge opening for unpulverized material insaid base plate ad jacent to the outer side of said grinding ring andsaid air entrance opening, a depending skirt on the outer side of saidgrinding ring beyond said drive yoke and having means for carryingmaterial depositing thereon tosaid discharge opening, and said baseplate having an upper inclined surface arranged to obstruct the inwardflow of material through the space below said skirt.

GEORGE B. EBERSOLE.

